Asphaltene Characterization: Sensitivity of Asphaltene Properties to Extration Techniques

Abstract

One step in asphaltene extraction is to wash the precipitated asphaltenes with the precipitant to remove trapped resinous material. To assess the effect of washing on asphaltene properties, asphaltenes were extracted with three different degrees of washing. Asphaltenes from three source oils (Athabasca, Cold Lake and Lloydminster) were examined. In all cases, increased washing decreased asphaltene yield and increased asphaltene density slightly. Increased washing increased molar mass and decreased the solubility of the extracted asphaltenes significantly.A new washing method using a soxhlet apparatus removed the greatest amount of resinous material and yielded asphaltenes with significantly different properties from conventionally washed asphaltenes. The asphaltenes from the different source oils exhibited similar properties after conventional washing. However, there were significant differences in their properties after applying the soxhlet method. Hence, the soxhlet method allows for a more sensitive comparison of asphaltenes.

Measurement and Modelling of Asphaltene Flocculation From Athabasca Bitumen

“…Asphaltenes were precipitated from the bitumen with the addition of n-heptane at a 40:1 volume ratio of heptane-to-bitumen and non-asphaltenic solids were removed by centrifugation. Details of the precipitation are provided elsewhere [7].…”

Regular solution model for asphaltene precipitation from bitumens and solvents

“…Densities and associated molar masses were previously measured for asphaltenes from dif-Ž ferent sources and for different extraction methods Yarranton and Masliyah, 1996;Yarranton et al, 2000;Akbarzadeh . et al, 2001;Alboudwarej et al, 2002 . The molar masses were measured with VPO at 50ЊC in toluene, but the density measurements were made at 23ЊC.…”

“…Details of the precipitation method Ž . are provided elsewhere Alboudwarej et al, 2002 . Most asphaltene samples contain nonasphaltenic solids including sand, clay and adsorbed organics. Solids were removed by dissolving asphaltenes in toluene and centrifuging Ž .…”

“…Molar masses of SARA fractions were measured using va-Ž por pressure osmometry as reported elsewhere Yarranton et al, 2000;Agrawala and Yarranton, 2001;Akbarzadeh et al, . 2001;Alboudwarej et al, 2002 . All measurements were made in toluene at 50ЊC.…”

PVT Investigation of Asphaltene Precipitation and Redissolution from Bitumens

“…Bench top experiments were conducted at ambient conditions using well established methods (5). The data from these experiments provide a benchmark to which the high temperature and pressure data can be compared.…”